1. Field of Invention
The present invention relates to a method for controlling the color of an LCD. More particularly, the present invention relates to a method for controlling the color of an LCD to improve dithering control in LCD devices.
2. Description of Related Art
Display hardware, including early computer video adapters and many modern LCDs used in mobile phones and inexpensive digital cameras, are only capable of showing a smaller color range than more advanced displays. One common application of dithering is to more accurately display graphics containing a greater range of color than the hardware is capable of showing.
The common dithering algorithm uses the spatial and temporal dithering to reduce the physical (hardware) cost and power consumption of LCDs. However, the scroll noise and flicker occurring on the LCD panel will sometimes occur while the dithering function is being executed, for example, the dithering function in the line inversion control mode.
Please refer to FIG. 1. FIG. 1 depicts a common 2-bit dithering algorithm in a 6-bit DAC to process 8-bit gray-level signal at line inversion control mode. When the input gray-level signal is 8-bit and the DAC is 6-bit, the 2-bit LSB (least significant bit) of the 8-bit gray-level signal is processed by the dithering algorithm. The 2-bit dithering algorithm generates four by four frames as a unit in spatial dithering and generates four frames as a unit in temporal dithering.
In addition, the polarity of each row on a frame is alternatively different and the polarity of each row is inverted at the next frame. Unfortunately, the variable polarity voltage of each controlled by VCOM may be vulnerable to error. Therefore, the brightness of point A and B are different. Moreover, the polarity of each row changes frame by frame. Hence, scroll noise and flicker occurs.
For instance, when XY (2-bit LSB) is 01, at frame N, column M, the offset pattern is at a negative polarity pixel. In addition, at frame N+1, column M, the offset pattern is at positive polarity pixel. However, the negative polarity voltage and the positive polarity voltage controlled by VCOM may not be symmetrical so that the brightness of the offset at column M is not identical in frame N and frame N+1. Hence, scroll noise and flicker occur in spatial and temporal dithering.
Therefore, it is desirable to improve the dithering algorithm to reduce the scroll noise and flicker in the LCD panel.